We usually use R3=1K for low voltage (12V) purposes. But if your voltage is high then you must use a higher value one. For R5 we usually use 18K-22K for battery full charge setting of 14V. We usually set this value by trial and error. We try to keep the hysteresis value at 2V so that if the battery full charge is set at 14V then due to 2V hysteresis, the comparator output will go low at 12V. If you use a relay at the comparator output and it chatters then you must increase the hysteresis value to 3V or more.
